1. Field of the Invention
The present invention relates to an apparatus for carrying a workpiece to and out of a press and, more particularly, to an apparatus for automatically carrying various workpieces which are to be pressed to a press disposed on a press line which continuously performs a pressing process.
2. Description of the Prior Art
With the automation of production lines, the loading of workpieces to be pressed is automated. On a press line constituted by 5 to 6 presses, an unloader for taking out the pressed workpieces and a loader for supplying workpieces to the press are used. The loader carries a workpiece which has been cut to shape to a press and the unloader carries the workpiece once pressed to another press, and in this manner each part of, e.g., a vehicle is produced through several pressing processes.
In a such a press line as shown in FIG. 3, a conveyor 12 travels between presses 10-1 and 10-2, and an unloader 18 which carries a workpiece 16 from a press die 14-1 of the press 10-1 and a loader 18" which carries the workpiece 16 into a press die 14-2 of the succeeding press 10-2 are provided. The unloader 18 pulls toward it, holds and places the workpiece 16 on a lift 20-1. The lift 20-1 vertically moved and places the workpiece 16 on the belt conveyor 12 at a predetermined control timing. The workpiece 16 is next held by a lift 20-2 on the side of the succeeding press 10-2. In this way, the workpiece carried from the press 10-1 is supplied to the press die 14-2 by the loader 18' in the same way as by the unloader 18.
FIG. 4 shows the structure of the loader 18' (unloader 18). The loader 18' is provided with an attachment 22 having two arms which hold and carry the workpiece 16. Two attracting means 24-1, 24-2 for holding the workpiece 36, such as magnets, are provided on the forward ends of the two arms, respectively.
The attachment 22 has a certain configuration and length depending on the configuration of a given workpiece in a given pressing design or on a given route of travel, and it is replaced by another attachment every time a different workpiece is to be pressed. The attachment 22 is connected to two parallel links 28-1 and 28-2 through a bayonet fitting 26.
The links 28-1 and 28-2 are pivotally attached to a slide plate 34 which slides on a slide rail 32 (in the direction indicated by the arrow b) on a loader (unloader) body 30. The link 28-1 is pivoted by a rocking arm 38 which engages a drive pin 36. The drive pin 36 is engaged with a cam plate 40 attached to the loader body 30. The cam plate 40 determines the route of travel of the attachment 22 and, hence, the route of travel of the workpiece 16. Thus, the rocking arm 38, which is driven by a drive motor 42, moves the attachment 22 on the route of travel indicated by the arrow 100. The attachment 22 constantly moves on the route which is fixed by the cam plate 40.
The loader 18' can move in the right and left direction with respect to the press 10-2. The loader body 30 is fixed to a body supporter 44 which is slidable on a longitudinal rail 46 attached to the press 10-1 or the like. A feed screw 50, which is connected to a longitudinal shaft drive motor 48, is engaged with a screw receiver 52 provided on the body supporter 44.
In this way, in the state in which the attachment 22 is movable in the longitudinal direction with respect to the press, the workpiece 16 is inserted into the press 10-1 on the predetermined route of travel 100 to be placed on the press die 14.
However, a conventional workpiece carrying apparatus of this kind is inconvenient in that the attachment 22 having two arms is coupled to the cam plate 40 so that the route of travel, which depends upon the cam plate, cannot be varied. If a workpiece of a particular pressing design is carried such as, for example, when a workpiece 16' indicated by the broken line in FIG. 4 is carried, the attachment is required to have one arm longer than the other one. In other words, it is necessary to prepare an attachment exclusively for each workpiece having a different configuration and to exchange it every time a workpiece having another configuration is to be pressed.
A high cost is involved in providing many attachments. Furthermore, the operation of changing attachments is troublesome and dangerous because it is conducted by a worker, and it thus constitutes a barrier to complete automation of a press line.
In addition, since the attachment is produced after confirmation by fitting actual parts, if the attachment is deformed by mistake during operation, it takes time to correct and restore the attachment to its original form, thereby making it impossible to immediately resume the operation of the press line.